Provide a hydroelectric power network for New Zealand from natural water resources

Hydroelectric power has been a key part of New Zealand's energy system for over 100 years. It supplies more than half of the country's energy needs.

The first schemes were built by mining companies at the height of the country's gold rush. Workers at a mine in the hills of Otago in South Island developed a small hydro plant to power equipment in 1886.

In May 1901 the New Zealand government built its first hydro plant – a small 100kW generator – at Okere Falls near Rotorua in the North Island.

The state's first major hydro power plant was the Lake Coleridge scheme which opened in the South Island in 1914 and took 3 years to build.

It was built to supply electricity to Christchurch, the largest city in the South Island, and credited with establishing the country's commitment to renewable hydro energy.

By the early 1960s most North Island hydro sites had been developed. The 1965 opening of the HDVC Inter-Island link – a 610km long high voltage transmission system connecting the country's islands – helped increase hydro capacity in South Island.

Public resistance to large scale hydroelectric generation grew in the 1960s with environmental campaigners criticising the effect big dams can have on the landscape and wildlife.

Although there are plans for some small schemes New Zealand's last major hydro project was the Clyde dam in South Island in 1993.

Hydroelectric power New Zealand

In the 1950s New Zealand's population grew rapidly and demand for electricity was increasing. The decision was made to start the Tongariro Power Scheme to meet this demand. The scheme created 3 power stations; Tokannu, Rangipo and Mangaio. Together they make up 3.5% of New Zealand's total annual electricity.

Difference hydroelectric power has made

By 2014 hydro generation was producing 57% of the country's total electricity needs. Peak production was in 1980 with 84% of the country's electricity generated by hydro.

The past 10 years have seen 50-60% of New Zealand's electricity generated by hydro power. Additionally, hydro provides 82% of electricity generated from renewable sources.

How the work was done

New Zealand has over 100 hydroelectric generating plants. Manapōuri power station in South Island is the country's biggest hydro station and its second biggest power plant.

Like many of New Zealand's hydro stations, Manapōuri uses terrain to create power. The station relies on a 230m drop between the western arm of Lake Manapōuri and the Doubtful Sound – a deep fiord 10km away - to generate electricity.

The construction of the underground power plant saw engineers digging out nearly 1.4m tonnes of hard rock to build the machine hall and a 10km tailrace tunnel.

A tailrace tunnel takes water away from an industrial application such as a turbine or waterwheel, after it's been used.

The station opened in 1972 with a second tailrace tunnel built in 2002 to increase generating capacity.

The station was the focus of a massive environmental campaign during planning and construction.

Engineers had wanted to raise Lake Manapōuri 30m by building a dam. Critics of the scheme said it would ruin the environment.

Almost 10% of New Zealanders signed a petition against the project and the dam was never built.

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What captured the public's imagination across the country was the prospect that a lake as beautiful as Manapōuri could be interfered with, despoiled and debased.

Neville Peat

author and photographer, on the Save Manapōuri campaign

Fascinating facts

New Zealand produced 40% of its energy from renewable resources in 2015. As well as hydro, the country has invested in geothermal, wind, solar and marine energy.

The country has a ready supply of geothermal energy as the earth's crust under the islands is relatively thin. Māori, New Zealand's indigenous people, have been cooking and washing with heat directly from the earth's core for centuries.

Geothermal energy currently provides 22% of New Zealand's primary energy supply, including more than 17% of its electricity.

People who made it happen

Clients: New Zealand government and municipal authorities

Thousands of engineers have worked on New Zealand's hydro schemes over the past century.